User set editorAssociations not show in openWith

[mjbvz]

Issue Type: Bug

Repo

1. Set

    "workbench.experimental.editorAssociations": [
        {
            "filenamePattern": "*.md",
            "viewType": "imagePreview.previewEditor",
        }
    ],

1. In explorer, right click on a md file and go to Open with

Bug
Preview editor is not listed in list of editors

VS Code version: Code - Insiders 1.39.0-insider (211fa02, 2019-09-11T06:12:03.831Z)
OS version: Darwin x64 18.7.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz (8 x 2200)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: enabled oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_deferred_display_list: disabled_off skia_renderer: disabled_off surface_synchronization: enabled_on video_decode: enabled viz_display_compositor: disabled_off webgl: enabled webgl2: enabled
Load (avg)	2, 2, 2
Memory (System)	16.00GB (0.05GB free)
Process Argv	-psn_0_2556528
Screen Reader	no
VM	20%

[RMacfarlane]

@mjbvz I'm not seeing an Open with option in the explorer context menu, has this been changed?